1. Field of the Invention
The present invention relates to a distributor-type fuel injection pump for use in a diesel engine, and more particularly to such fuel injection pump having an improved lubrication oil supply mechanism.
2. Prior Art
Bosch pumps or distributor-type fuel injection pumps generally comprise a feed pump disposed in a pump body adjacent to the rear side thereof and a cam chamber defined between the fuel pump and a head portion of the pump body. A drive shaft and a plunger are coupled together within the cam chamber through a cam so that the plunger makes rotational and reciprocating motions simultaneously, in unison with the rotation of the drive shaft.
In general, the cam chamber is utilized as a fuel chamber for receiving a fuel delivered from the fuel pump. The fuel thus received lubricates the cam and other movable components in the cam chamber. However, because of its low viscosity, the fuel gives only an insufficient lubrication which would result in a short service time of the pump. With the foregoing difficulty in view, it has been a long desire to devise a pump wherein a lubrication oil is supplied into the cam chamber for exclusively lubricating the cam and other components in the cam chamber.
One prior attempt proposed to meet this desire is disclosed in Japanese Patent Laid-open Publication No. 56-154135, wherein a magnetic valve is disposed on the head portion of a fuel injection pump body for controlling the flow of a fuel delivered from a pump working chamber defined between a cylinder and a plunger. With the magnetic valve thus provided, a governor and a control sleeve are displaced and it becomes possible to introduce a lubrication oil into the cam chamber. According to another attempt shown in Japanese Patent Laid-open Publication No. 56-88957, a fuel injection pump includes a cam chamber which is divided into a first compartment for receiving a cam and a second compartment for receiving a control sleeve, a lubrication oil being delivered into the first compartment.
In the aforementioned fuel injection pumps, the lubrication oil is supplied directly into the cam chamber or the first compartment through an inlet defined therein, without agency of any control means for adjusting the supply of the lubrication oil. With this construction, it is likely that an excess amount of lubrication oil is introduced into the cam chamber or the first compartment. This difficulty may be overcome by a control means separately provided for controlling the supply of the lubrication oil. However, provision of such a control means would cause another drawback such that the number of parts or components becomes large and hence the fuel injection pump is complex in structure and hence is complex in construction.